From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B23FDC2C5; Mon, 19 Jun 2023 15:43:38 +0000 (UTC) Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCF8B183; Mon, 19 Jun 2023 08:43:34 -0700 (PDT) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=hengqi@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0VlYSrVC_1687189409; Received: from localhost(mailfrom:hengqi@linux.alibaba.com fp:SMTPD_---0VlYSrVC_1687189409) by smtp.aliyun-inc.com; Mon, 19 Jun 2023 23:43:30 +0800 Date: Mon, 19 Jun 2023 23:43:29 +0800 From: Heng Qi To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Jason Wang , Xuan Zhuo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend Subject: Re: [PATCH net-next 4/4] virtio-net: remove F_GUEST_CSUM check for XDP loading Message-ID: <20230619154329.GD74977@h68b04307.sqa.eu95> References: <20230619105738.117733-1-hengqi@linux.alibaba.com> <20230619105738.117733-5-hengqi@linux.alibaba.com> <20230619071347-mutt-send-email-mst@kernel.org> <20230619124154.GC74977@h68b04307.sqa.eu95> <20230619103208-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230619103208-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Mon, Jun 19, 2023 at 10:33:44AM -0400, Michael S. Tsirkin wrote: > On Mon, Jun 19, 2023 at 08:41:54PM +0800, Heng Qi wrote: > > On Mon, Jun 19, 2023 at 07:16:20AM -0400, Michael S. Tsirkin wrote: > > > On Mon, Jun 19, 2023 at 06:57:38PM +0800, Heng Qi wrote: > > > > Lay the foundation for the subsequent patch > > > > > > which subsequent patch? this is the last one in series. > > > > > > > to complete the coexistence > > > > of XDP and virtio-net guest csum. > > > > > > > > Signed-off-by: Heng Qi > > > > Reviewed-by: Xuan Zhuo > > > > --- > > > > drivers/net/virtio_net.c | 4 +--- > > > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > index 25b486ab74db..79471de64b56 100644 > > > > --- a/drivers/net/virtio_net.c > > > > +++ b/drivers/net/virtio_net.c > > > > @@ -60,7 +60,6 @@ static const unsigned long guest_offloads[] = { > > > > VIRTIO_NET_F_GUEST_TSO6, > > > > VIRTIO_NET_F_GUEST_ECN, > > > > VIRTIO_NET_F_GUEST_UFO, > > > > - VIRTIO_NET_F_GUEST_CSUM, > > > > VIRTIO_NET_F_GUEST_USO4, > > > > VIRTIO_NET_F_GUEST_USO6, > > > > VIRTIO_NET_F_GUEST_HDRLEN > > > > > > What is this doing? Drop support for VIRTIO_NET_F_GUEST_CSUM? Why? > > > > guest_offloads[] is used by the VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET > > command to switch features when XDP is loaded/unloaded. > > > > If the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is negotiated: > > 1. When XDP is loaded, virtnet_xdp_set() uses virtnet_clear_guest_offloads() > > to automatically turn off the features in guest_offloads[]. > > > > 2. when XDP is unloaded, virtnet_xdp_set() uses virtnet_restore_guest_offloads() > > to automatically restore the features in guest_offloads[]. > > > > Now, this work no longer makes XDP and _F_GUEST_CSUM mutually > > exclusive, so this patch removed the _F_GUEST_CSUM from guest_offloads[]. > > > > > This will disable all of guest offloads I think .. > > > > No. This doesn't change the dependencies of other features on > > _F_GUEST_CSUM. Removing _F_GUEST_CSUM here does not mean that other > > features that depend on it will be turned off at the same time, such as > > _F_GUEST_TSO{4,6}, F_GUEST_USO{4,6}, etc. > > > > Thanks. > > Hmm I don't get it. > > static int virtnet_restore_guest_offloads(struct virtnet_info *vi) > { > u64 offloads = vi->guest_offloads; > > if (!vi->guest_offloads) > return 0; > > return virtnet_set_guest_offloads(vi, offloads); > } > > is the bit _F_GUEST_CSUM set in vi->guest_offloads? No, but first we doesn't clear _F_GUEST_CSUM in virtnet_clear_guest_offloads(). If VIRTIO_NET_F_CTRL_GUEST_OFFLOADS is negotiated, features that can be dynamically controlled by the VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET command must also be negotiated. Therefore, if GRO_HW_MASK features such as _F_GUEST_TSO exist, then _F_GUEST_CSUM must exist (according to the dependencies defined by the spec). Now, we only dynamically turn off/on the features contained in guest_offloads[] through XDP loading/unloading (with this patch, _F_GUEST_CSUM will not be controlled), and _F_GUEST_CSUM is always on. Another point is that the virtio-net NETIF_F_RXCSUM corresponding to _F_GUEST_CSUM is only included in dev->features, not in dev->hw_features, which means that users cannot manually control the switch of _F_GUEST_CSUM. > > Because if it isn't then we'll try to set _F_GUEST_TSO > without setting _F_GUEST_CSUM and that's a spec > violation I think. As explained above, we did not cause a specification violation. Thanks. > > > > > > > > > > > > @@ -3522,10 +3521,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > > > > virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) || > > > > virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) || > > > > virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO) || > > > > - virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM) || > > > > virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_USO4) || > > > > virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_USO6))) { > > > > - NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing GRO_HW/CSUM, disable GRO_HW/CSUM first"); > > > > + NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing GRO_HW, disable GRO_HW first"); > > > > return -EOPNOTSUPP; > > > > } > > > > > > > > -- > > > > 2.19.1.6.gb485710b